This Is How the Sun Causes Skin Cancer, According to Science

Science tells us that sun exposure could lead to skin cancer. But exactly how basking in the sun's rays can lead to scary skin cancers, like melanoma, hasn't totally been understood — until now. Scientists at Cornell University just discovered exactly how UV rays trigger the formation of melanoma — the deadliest form of skin cancer.

Here's what scientists already knew: Skin pigment cells are called melanocytes. When the sun — a.k.a. ultraviolet radiation — hits your skin, it activates your melanocytes, triggering them to release pigment to protect you from harmful rays, according to the Cornell Chronicle. In other words, you get a tan.

We also know that UV rays can damage skin cells. "UV light creates free radicals that damage the skin cells and their DNA," Joshua Zeichner, director of cosmetic and clinical research in dermatology at Mount Sinai Hospital in New York City, tells Allure. "With enough DNA damage, the cells can become uncontrolled and become cancerous."

The new study, published this month in the journal Cell Stem Cell, found that once a melanocyte cell has become damaged through genetic mutations, increased sun exposure triggers the development of a tumor. In other words, in a healthy cell, the sun will trigger a tan — but in a damaged cell, those same rays will trigger a tumor.

"If you had mutations that were sufficient for melanoma, everything would be fine until you went out and got a sunburn," Andrew White, assistant professor of biomedical sciences at Cornell's College of Veterinary Medicine and a senior author on the study, said in an interview with the Cornell Chronicle. "The stimuli that would normally just give you a tanning response could, in fact, start a melanoma instead."

The study also found a possible way to prevent damaged cells from turning into the scary skin disease — but it's not the type of treatment you can pick up at the drugstore. Researchers suspected a specific gene called Hgma2 was responsible for triggering the tanning response in melanocyte stem cells. They then took mice engineered with the skin cell mutations that can morph into cancer and exposed them to low-levels of UV light after removing the Hgma2 gene from one group of mice. They found that the group with the gene removed didn't develop melanomas, while the other group did. In the future, targeting this gene could be a way to prevent melanomas from ever happening.

So, what does this all mean when it comes to protecting your skin from the sun today? "The results of this study show that even damaged cells may need an additional trigger to become a skin cancer," says Zeichner. So while damaging your skin cells by neglecting your sunscreen routine is a giant no-no, you can still stop mutated cells from turning into a full-on melanoma by doubling down on sun protection. "This is one more reason to wear a broad spectrum SPF every day both to minimize sun damage from developing and prevent already damaged cells from transforming into a cancer," Zeichner says.